1. Field of the Invention
A system for monitoring and controlling exothermic reactions in an ion exchange process and more particularly for use in the ion exchange purification of solutions of hydroxylamine.
2. Description of the Prior Art
The use of ion exchange for purifying hydroxylamines is well known. However, resin conditioning and regeneration in the purification processes of the prior art have not dealt with the reduction of trace metals or the possibility of exothermic reactions resulting from the decomposition of hydroxylamine or other organic compounds which may be unstable.
Unstablized solutions of hydroxylamine are inherently prone to decomposition, since the compound functions both as an oxidizing agent and a reducing agent. It decomposes by internal oxidation-reduction to form gaseous products, i.e. ammonia and nitrogen or oxides of nitrogen and water. The xe2x80x9credoxxe2x80x9d decomposition is accelerated by a high pH and the presence of catalytic amounts of certain multivalent heavy metals such as iron, nickel, copper, manganese and chromium. Other compounds such as mercaptans, typical oxidizing and reducing agents, oxygen and heat can also initiate complete decomposition of hydroxylamine which can be rapid under certain condition such as high levels of catalyic trace metals, elevated temperatures plus absence of an effective stablizer.
Additionally, the order of ion exchange is critical to maintaining stability of the hydroxylamine within the ion exchange cylinder. It has been found that anion exchange followed by cation exchange can lead to delayed, but then rapid decomposition of hydroxylamine and produce consequences of significant pressure build-up within the cation resin cylinder which can lead to a xe2x80x9cburstingxe2x80x9d of the cylinder, and cylinder head. Errors by workers in following the prescribed ion exchange order can result in such pressure build-up and potential xe2x80x9cburstsxe2x80x9d.
The decomposition of hydroxylamine is an exothermic reaction which propagates the continuing decomposition process. The production of heat during this decomposition of the hydroxylamine is effective at producing further decomposition, which in turn may produce additional heat. Once effectively initiated, the decomposition can become auto-catalytic under certain conditions.
In accordance with an aspect of the present invention, there is provided a system for monitoring and controlling any liquid containing a composition or reactants capable of undergoing an exothermic reaction in an ion exchange process which comprises a xe2x80x9cmonitorxe2x80x9d means for receiving and monitoring a temperature signal from each ion exchange unit and for providing processible values indicative of the magnitude of the temperature, data processing means for reading the temperature signal in a pre-established processible manner, means for detecting if one or more of the ion exchange units exceeds pre-established thermal limits indicating that an exothermic reaction is taking place and thereby providing control signals for controlling the temperature of the ion exchange process and for activating either visual or audible alarms or both, means for controlling the flow of an inert quenching fluid into each unit which exceeds the pre-established temperature limits to quench the reaction and lower the temperature of each overheated unit to acceptable temperature levels and control means for automatically resetting the means for controlling the flow of the inert fluid and the alarm means.
An important feature of the invention is that the monitor means continuously monitors the temperature signals and continuously provides a data processing value indicative of the temperature from each ion exchange unit and is operatively associated with a data processing means. The temperatures of each unit are detected through a series of thermal probes which are insulatively attached and in full contact with the outside top and bottom of each ion exchange unit and are operatively connected through a monitor means to digital thermostats. The monitor means provides a digital read-out for each ion exchange unit, thus, the exact location of each problem xe2x80x9chotxe2x80x9d unit can be pin-pointed. The digital thermostats each have manually set temperature limits in response to which of the various components of the system of this invention are activated.
In accordance with the present invention, the system of monitoring and regulating exothermic reactions in an ion exchange process can be useful for any liquid containing a compound, composition or reactants capable of undergoing an exothermic reaction such as the simple mixing of acid or caustic with water. More particularly, this invention is directed to the ion exchange purification of an aqueous or non-aqueous solution containing hydroxylamine or at least a neutralized hydroxylamine salt. As mentioned above, the solutions of unstablized hydroxylamine are inherently prone to decomposition and must be closely monitored especially in a closed vessel to avoid an excessive build-up of gases and, therefore, pressure with an attendant increase in temperature. These gaseous decomposition products can produce pressures within closed containers which can yield xe2x80x9cexplosivexe2x80x9d pressures over time dangerous to operators and destructive to equipment.
The system of the present invention may be operated in an automatic mode or in a manual mode.
A method for operating the system and for setting operating limits (i.e. xe2x80x9calertxe2x80x9d and xe2x80x9calarmxe2x80x9d limits) is also disclosed.
It is, therefore, a primary object of the invention to provide a system for monitoring and controlling liquid temperature in a medium containing a compound composition or reactants capable of undergoing an exothermic reaction whether or not gaseous products are reduced.
It is another object of the invention to provide a system for monitoring and controlling (i.e., through an automatically activated quenching system) an excessive thermal build-up in an ion exchange process treating a liquid containing a compound, composition or reactants capable of undergoing an exothermic reaction whether or not gaseous products are produced.
It is a further object of the invention to provide a system which can pin-point an excessive thermal build-up in an ion exchange treatment process beyond a pre-set temperature limit containing a solution capable of undergoing an exothermic reaction whether or not gaseous products are produced.
It is a further object of the invention to provide a system which can pin-point an excessive thermal build-up from an exothermic reaction beyond a pre-set temperature limit to a specific location in a series of ion exchange units and provide means to quench the exothermic reaction.
It is yet a further object to provide a process to monitor and regulate a liquid containing a compound or composition capable of undergoing an exothermic reaction while in storage.
Still another object is to provide a system to monitor and regulate the ion exchange purification of solutions of hydroxylamine.
It is a still further object of the invention to provide a purification system with a reduced hazard of closed container pressure xe2x80x9cburstingxe2x80x9d (i.e., explosion) from continuous decomposition of hydroxylamine over time within a closed or possibly vented ion exchange unit.
These and other objects of the present invention will become apparent to those skilled in the art upon a reading and understanding of the specification together with the attached drawing.